Somehow a setting got changed where "Unapproved Members" were gaining "post" access to too many forums.
I've just upgraded the software a couple weeks ago - and I'm still tuning the spam protection and so on.
A small statistic - for all the posts that got through, the spam filter so far has flagged over 200 posts and about 60 registrations that were blocked already...
Forum spammers are usually robots - that wind up a forum in their sights based on google "dorks" to find sites that use the same software - then they craft scripts that manage to register, bypass the reCaptcha, bypass the "other registration hurdles", navigate to a forum, and begin spamming posts...
It's a big pain in the ass to contend with...